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Öğe 4Nx Non-Isolated and Non-Inverting Hybrid Interleaved Multilevel Boost Converter Based on VLSIm Cell and Cockroft Walton Voltage Multiplier for Renewable Energy Applications(Ieee, 2016) Bhaskar, Mahajan Sagar; Padmanaban, Sanjeevikumar; Blaabjerg, Frede; Norum, Lars E.; Ertas, Ahmet H.In this treatise, 4Nx hybrid Non Inverting & Non Isolated (NI-NI) DC-DC interleaved multi-level boost converter (4Nx IMBC) for renewable energy applications is proposed. The proposed 4Nx IMBC is derived by coalescing the feature of 2Nx DC-DC Interleaved Multi-level Boost Converter (2Nx IMBC), voltage-lift-switched-inductor-modified (VLSIm Cell) and Cockcroft Walton (CW) voltage multipliers. The 4Nx converter provides 4N times more conversion voltage ratio compared to conventional boost converter where N denotes the number of output stages of the 4Nx IMBC. To make renewable energy sources applicable at user end its DC voltage magnitude needs to be incremented with high conversion. Existing and recently proposed DC-DC converter are not sufficiently expert to employ practically, because of stability issues, high duty cycle and high ripple in the output. To overcome the conversion ratio problem isolated boost DC-DC converter are in use but it makes circuitry bulky and costly because of transformer and several coupled inductors. The converter topology proposed in this treatise reduces the output ripple and overcome the problem mentioned above without exploiting extreme values of duty cycle or transformers. Simulations results of proposed circuitry are presented which verify the analysis, function, working modes & feasibility of proposed circuitry converter.Öğe Analysis of enhancement in available power transfer capacity by STATCOM integrated SMES by numerical simulation studies(Elsevier - Division Reed Elsevier India Pvt Ltd, 2016) Ananthavel, Saraswathi; Padmanaban, Sanjeevikumar; Shanmugham, Sutha; Blaabjerg, Frede; Ertas, Ahmet H.; Fedak, ViliamPower system researches are mainly focused in enhancing the available power capacities of the existing transmission lines. But still, no prominent solutions have been made due to several factors that affect the transmission lines which include the length, aging of the cables and losses on generation, transmission and distribution etc. This paper exploited the integration of static synchronous compensator (STATCOM) and superconducting magnetic energy storage (SMES) which is then connected to existing power transmission line for enhancing the available power transfer capacity (ATC). STATCOM is power electronic voltage source converter (VSC) which is connected to the transmission system for shunt reactive power and harmonics compensation. SMES is a renowned clean energy storage technology. Feasibility of the proposed power system can control the real as well as reactive power flow independently between the transmission lines and STATCOM-(SMES) units. Complete proposed power system is implemented in numerical simulation software (Matlab/Simulink) and its performance is validated based on obtained investigation results. (C) 2016, Karabuk University. Publishing services by Elsevier B.V.Öğe Analysis of Wavelet Controller for Robustness in Electronic Differential of Electric Vehicles: An Investigation and Numerical Developments(Taylor & Francis Inc, 2016) Daya, Febin J. L.; Sanjeevikumar, Padmanaban; Blaabjerg, Frede; Wheeler, Patrick W.; Ojo, Joseph Olorunfemi; Ertas, Ahmet H.In road transportation systems, differential plays an important role in preventing the vehicle from slipping on curved tracks. In practice, mechanical differentials are used, but they are bulky because of their increased weight. Moreover, they are not suitable for electric vehicles, especially those employing separate drives for both rear wheels. The electronic differential constitutes recent technological advances in electric vehicle design, enabling better stability and control of a vehicle on curved roads. This article articulates the modeling and simulation of an electronic differential employing a novel wavelet transform controller for two brushless DC motors ensuring drive in two right and left back driving wheels. Further, the proposed work uses a discrete wavelet transform controller to decompose the error between actual and command speed provided by the electronic differential based on throttle and steering angle as the input into frequency components. By scaling these frequency components by their respective gains, the obtained control signal is actually given as input to the motor. To verify the proposal, a set of designed strategies were carried out: a vehicle on a straight road, turning right and turning left. Numerical simulation test results of the controllers are presented and compared for robust performance and stability.Öğe A bio-inspired novel optimization technique for reactive power flow(Elsevier - Division Reed Elsevier India Pvt Ltd, 2016) Christy, Ananthy; Raj, Perianayagam Ajay-D-Vimal; Padmanaban, Sanjeevikumar; Selvamuthukumaran, Rajasekar; Ertas, Ahmet H.In the arena of power system operation and planning, the optimal reactive power flow (ORPF) plays a pivotal role, wherein the application of classical techniques poses issues in obtaining the optimal solutions and hence is usually employed with the meta-heuristic and/or bio-inspired techniques, with a view to converge swiftly towards an optimal solution. Usually, ORPF can have uneven, intermittent objectives and multi-constraint functions; and such intricacies of ORPF can best be suppressed by employing a combination of nature-inspired algorithms as a process of hybridization. Thus, in this paper, an approach has been endeavoured to hybridize the Biogeography based optimization (BBO) with that of the predator-prey optimization (PPO), so as to be rightfully termed as adaptive biogeography based predator-prey optimization (ABPPO). In such a way, this paper elucidates a novel hybrid technique that includes adaptive mutation combined with predator-prey pattern for attaining the global optimal point. In adaptive mutation scheme, the diversity measure of distance-to-average point is the predominant feature that dodges the supremacy of extremely feasible solutions throughout enhancing the population diversity. The predators explore around the elite prey in a determined way, whereas the preys search the solution space so as to evade from the predators. This tool improves the utilization and searching abilities of the BBO exploration procedure, thereby offers a mean of evading from the suboptimal point and imposes the populace to attain at the global best point. The efficacy of this hybrid scheme is validated against the standard test cases of IEEE-30 and IEEE-57 bus systems. The results show the efficiency and vitality of the proposed method. (C) 2016 Karabuk University. Publishing services by Elsevier B.V.Öğe Brain tumor detection using monomodal intensity based medical image registration and MATLAB(Tubitak Scientific & Technological Research Council Turkey, 2016) Irmak, Emrah; Ercelebi, Ergun; Ertas, Ahmet H.The registration concept is one of the most important and popular aspects of digital image processing. Using suitable computer programming techniques and transformation between two images, a new much more informative image can be found. In this paper, three important and basic medical image registration (MIR) methods, namely MIR by maximization of mutual information, MIR using cross correlation (Fourier transform approach), and MIR by minimization of similarity metric, were proposed and accordingly two comprehensive applications were performed using MIR by minimization of the similarity metric, which uses the sum of the squared differences metric as a metric and the regular step gradient descent optimizer as an optimizer. What is more, MR images of two patients who had brain tumors are registered with different MR images of the same patients at a different time so that growthiness of the tumor inside the patient's brain can be investigated. It is thought that this paper will provide a comprehensive reference source for researchers involved in MIR because this paper contains not only a powerful explanation of three methods of medical image registration but also provides two experimental results using MIR by minimization of the similarity metric.Öğe A clinically feasible kinematic assessment method of upper extremity motor function impairment after stroke(Elsevier Sci Ltd, 2016) Ozturk, Ali; Tartar, Ahmet; Huseyinsinoglu, Burcu Ersoz; Ertas, Ahmet H.The development of feasible kinematic assessment methods of upper extremity motor function impairment after stroke is clinically extremely important in physiotherapy and rehabilitation engineering. Microsoft Kinect has a potential of a low-cost and compact solution for clinical based assessment of the upper limb motor function after stroke. However, the reliability of Microsoft Kinect in the upper limb motor function assessment has not been well established. Therefore, there is a hesitation in usage of Microsoft Kinect for clinical applications. It is expected that any measurement procedure has the capability to differentiate between pathological and normal performance. On the other hand, the identification of the kinematic metrics that best evaluate impairment of upper-extremity motor function is a key problem of any measurement protocol. Primary objective of our study is, by differentiating pathological performance from the healthy performance and identifying the kinematic metrics that best evaluate the impairment, to demonstrate the robustness/usability of Microsoft Kinect in kinematic analysis of motor performance of stroke patients. We compared the kinematic metrics of the forward reaching movement obtained data recorded from Microsoft Kinect between three stroke patients and two healthy subjects based on the Principal Component Analysis (PCA). In the study, we have defined a new inter-joint coordination index (IJCI) based on PCA to capture inter-joint coordination dynamic of reaching movement in addition to other metrics those have been previously defined and used in literature to quantify upper limb impairment. We observed that the IJCI has significant importance to detect impairment of upper-extremity motor function during a forward reaching task and to discriminate stroke patients from healthy controls. We hope that this paper will promote the acceptance of objective kinematic analysis into routine rehabilitation practices. (C) 2015 Elsevier Ltd. All rights reserved.Öğe Creep simulation and comparison of micro-CT-based FE model of porcine and human cancellous bone(Taylor & Francis Ltd, 2013) Ertas, Ahmet H.[No abstract available]Öğe Design of fiber reinforced laminates for maximum fatigue life(Elsevier Science Bv, 2010) Ertas, Ahmet H.; Sonmez, Fazil O.Composite materials are used in many structural applications due to their superior properties, e. g., strength-to-weight ratio. Composite structures also offer great flexibility and stiffness in design, allowing change of the material system in many ways like number of fibers, different lay-up configurations, etc. With the increased use of composites it has been understood that their deformations in terms of fatigue is more complex than that of metals. Because of the major deficiencies in life prediction methodologies for composite materials resulting from their complexities, composite structures, used in fatigue applications for example, are generally over-designed to eliminate catastrophic and fatal failures and are therefore heavier and more costly. In this study, a methodology was proposed to find globally optimum designs of composite laminates subject to given in-plane loads for maximum fatigue life. For this purpose, a parametric fatigue life prediction model, proposed by Fawaz and Ellyin, was coupled with a global optimization technique called Direct Simulated Annealing (DSA) which is the improved version of Simulated Annealing (SA). The number of distinct fiber orientation angles and the number of plies each lamina contains were predetermined. The fiber orientation angles in each layer were taken as design variables and determined in the design process. A computer code was developed in ANSYS parametric language and results were obtained for different configurations and loading conditions. A number of problems were solved to demonstrate the effectiveness and reliability of the proposed method. (C) 2010 Published by Elsevier Ltd.Öğe Design optimization of fiber-reinforced laminates for maximum fatigue life(Sage Publications Ltd, 2014) Ertas, Ahmet H.; Sonmez, Fazil O.Composite structures are usually subjected to fluctuating loads in service leading to fatigue failure. Because it is one of the main failure modes, fatigue behavior of composites has been extensively studied to be able to design fatigue-resistant composite structures. However, little attention has been paid to their design optimization under fatigue loading. In this study, a methodology is proposed to find the optimum fiber orientation angles of composite laminates under various in-plane loads to achieve maximum fatigue life. Fawaz-Ellyin's model is used to predict the fatigue life of the laminates. A variant of simulated annealing algorithm is used as the search algorithm in the optimization procedure. A number of problems are solved to demonstrate the effectiveness of the proposed method.Öğe Design optimization of spot welded structures to attain maximum strength(Techno-Press, 2015) Ertas, Ahmet H.This study presents design optimization of spot welded structures to attain maximum strength by using the Nelder-Mead (Simplex) method. It is the main idea of the algorithm that the simulation run is executed several times to satisfy predefined convergence criteria and every run uses the starting points of the previous configurations. The material and size of the sheet plates are the pre-assigned parameters which do not change in the optimization cycle. Locations of the spot welds, on the other hand, are chosen to be design variables. In order to calculate the objective function, which is the maximum equivalent stress, ANSYS, general purpose finite element analysis software, is used. To obtain global optimum locations of spot welds a methodology is proposed by modifying the Nelder-Mead (Simplex) method. The procedure is applied to a number of representative problems to demonstrate the validity and effectiveness of the proposed method. It is shown that it is possible to obtain the global optimum values without stacking local minimum ones by using proposed methodology.Öğe Design optimization of spot-welded plates for maximum fatigue life(Elsevier Science Bv, 2011) Ertas, Ahmet H.; Sonmez, Fazil O.Resistance spot welding is the most preferred and widely used method for joining metal sheets in automotive and many other industrial assembly operations. Spot-welded joints are usually the weakest parts of structures leading to fatigue failure under fluctuating loads. Increasing the fatigue strength of the joints through geometrical changes will also increase the overall integrity of the whole structure. In this study, a methodology is proposed to find the optimum locations of spot welds and the optimum overlapping length of the joined plates for maximum fatigue life. Minimum weld-to-weld and weld-to-edge distances recommended by the industry are considered as side constraints. The total strain life equation is used to predict the fatigue life. In order to use this model, the strain state in the structure developed under cyclic loading is required. For this purpose, a nonlinear finite element analysis is carried out, taking into account residual stresses due to localized plastic deformations around the spots. Nelder-Mead (Sequential Simplex) is employed as the search algorithm in the optimization procedure. A number of problems are solved to demonstrate the effectiveness of the proposed method. (C) 2010 Elsevier B.V. All rights reserved.Öğe DETERMINATION OF FATIGUE AND STATIC STRENGTH OF SCOTS PINE AND BEECH WOOD(Slovak Forest Products Research Inst, 2015) Yildirim, Mehmet Nuri; Uysal, Burhanettin; Ozcifci, Ayhan; Ertas, Ahmet H.In this study, fatigue and static strength of Scots pine (Pinus sylvestris L.) and beech (Fagus orientalis L.) woods were investigated. The fatigue and static strength were conducted using a three point bending test-rig. The specimens were prepared according to ISO 3129 (1975) and fatigue and static bending test were carried out according to ISO 3133 (1975). The fatigue test was carried out at 80, 70, 60, 50 and 40 % stress level that corresponded to specific percentage of material's ultimate strength modulus of rupture (MOR). However the microstructures of fatigue failures were observed by using scanning electron microscope (SEM). The results were indicated that, the fatigue life of Scots pine wood amounted to over 1 million cycle when the stress level was 40 % of MOR for Scots pine and 50 % MOR for Beech. In general, fatigue life decreased as stress level increased and vice versa. The allowable design stress is based on some percentage of MOR for furniture design. On this account, the allowable design stresses for Beech and Scots pine could be set at 50 and 40 % respectively.Öğe Dual Mode Control of Inverter to Integrate Solar-Wind Hybrid fed DC-Grid with Distributed AC grid(Ieee, 2016) Awasthi, Abhishek; Venkitusamy, Karthikeyan; Selvamuthukumaran, Rajasekar; Padmanaban, Sanjeevikumar; Siano, Pierluigi; Ertas, Ahmet H.This paper presents integration of solar-wind hybrid fed DC-grid to distributed AC grid. Generally, the renewable hybrid energy systems use two or more energy sources to supply power to the dc grid. In case of insufficient power generation or excessive load demand, in order to supply power to DC loads, it must integrate with AC grid. As dc loads increase in number, complexity increases and tighter voltage regulation is required. This paper presents dual mode control operation of inverter which integrates the solar and wind power fed dc bus to the single phase ac distribution system. The inverter can be operated in hysteresis current control when power is fed from DC grid to AC distributed grid and in AC-DC boost rectifier mode otherwise. The detailed operation of dual mode control of inverter is described in this paper. The effectiveness of the proposed system has been verified through simulation studies using MATLAB/SIMULINK.Öğe Dual MPPT algorithm for dual PV source fed Open-End Winding Induction Motor Drive for pumping application(Elsevier - Division Reed Elsevier India Pvt Ltd, 2016) Jain, Sachin; Ramulu, Chinthamalla; Padmanaban, Sanjeevikumar; Ojo, Joseph Olorunfemi; Ertas, Ahmet H.This paper presents a single-stage solution for a dual Maximum Power Point Tracking (MPPT) technique for a solar Photovoltaic (PV) fed water pumping system. The proposed solar PV fed pumping system uses a three-phase Open-End Winding Induction Motor (OEWIM) coupled to a centrifugal water pump. The OEWIM is connected via two time tested two-level three-phase inverters powered by two independent solar PV arrays. These two PV arrays can be configured independently and the employed dual MPPT algorithm operate the two PV sources at or near maximum power point (MPP) irrespective of its configuration. Usage of different array configurations may help in attaining more number of levels (greater than or equals to three) in the inverter output voltage (OEWIM phase voltage). Furthermore, the system is operated using decoupled Pulse Width Modulation (PWM) technique with V/f control along with the proposed dual MPPT technique. The maximum power extracted by the dual MPPT algorithm from two PV sources is optimally utilized by the OEWIM. This can be supported by the low slip value at all the operating conditions. The detailed analysis of proposed system and the simulation results are presented. (C) 2016 Karabuk University. Publishing services by Elsevier B.V.Öğe Finite Element Simulation of a Mercantile Vessel Shipboard Under Working Conditions(Elsevier Science Bv, 2014) Ertas, Ahmet H.; Alkan, Veysel; Yilmaz, Ahmet FatihDespite the availability of other transport methods such as land and air, marine transportation is the most preferred and widely used transportation method in the world because of its economical advantages. Due to the economical advantages, ship based studies have gained importance especially in recent years. In order to design safe, ergonomic and at the same time economic ships or vessels, both numerical and experimental methods have to be taken into account. Large-scale structural modeling like the cases in ships, on the other hand, typically relies on Finite Element Analysis (FEA) techniques. With the widespread use of Finite Element Methods (FEM) in the field of Computer Aided Design (CAD) engineering, it is possible to increase the strength of a mercantile vessel shipboard. As a consequence, in this study, the strength of a mercantile vessel shipboard has been investigated under working conditions by using ANSYS package program. The results of this study can provide the designer with some guidelines in designing shipboard of mercantile vessels. (C) 2014 The Authors. Published by Elsevier Ltd.Öğe High-Voltage DC-DC Converter Topology for PV Energy UtilizationInvestigation and Implementation(Taylor & Francis Inc, 2017) Padmanaban, Sanjeevikumar; Blaabjerg, Frede; Wheeler, Patrick; Ojo, Joseph Olorunfemi; Ertas, Ahmet H.This paper exploited the utilization of photovoltaic (PV) energy system with high-voltage (HV) output DC-DC converter. Classical boost converters are used for both renewable energy integration and HV applications, but limited by reducing output/efficiency in performance. Moreover, as parasitic elements suppress the power transfer ratio, converter needs to maximize the PV energy utilization. This investigation study focused to include additional parasitic elements (voltage-lift technique) to a standard DC-DC buck converter and to overcome all the above drawbacks to maximize the PV power generation. The proposed power circuitry substantially improves the output power gain transfer ratio and a prototype hardware module is implemented using industrial standard DSP TMS 320F2812. Numerical simulation development followed by an experimental prototype implementation is carried out in this investigation. A set of numerical and experimental results is provided in this paper, which show close conformity with the theoretical background.Öğe Numerical implementation of wavelet and fuzzy transform IFOC for three-phase induction motor(Elsevier - Division Reed Elsevier India Pvt Ltd, 2016) Padmanaban, Sanjeevikumar; Daya, Febin J. L.; Blaabjerg, Frede; Mir-Nasiri, Nazim; Ertas, Ahmet H.This article elaborates the numerical implementation of a novel, indirect field-oriented control (IFOC) for induction motor drive by wave-let discrete transform/fuzzy logic interface system unique combination. The feedback (speed) error signal is a mixed component of multiple low and high frequencies. Further, these signals are decomposed by the discrete wave-let transform (WT), then fuzzy logic (FL) generates the scaled gains for the proportional-integral (P-I) controller parameters. This unique combination improves the high precision speed control of induction motor during both transient as well as steady-state conditions. Numerical simulation model is implemented with proposed control scheme using Matlab/Simulink software and obtained results confirm the expectation. (C) 2015, Karabuk University. Production and hosting by Elsevier B.V.Öğe Optimization of fiber reinforced laminates for maximum fatigue life using Particle Swarm Optimization(Elsevier Science Bv, 2012) Ertas, Ahmet H.Composites are commonly used materials in many structural applications because of their advantageous like lightness or strength-to-weight ratio. With the increased use of composites it has been understood that their deformations in terms of fatigue is more complex than that of metals. Although fatigue behavior of composites has been studied extensively, little attention was paid to optimization of composites under fatigue. In this study, an improved methodology is proposed to find globally optimum designs of composite laminates subject to given in-plane loads for maximum fatigue life. For this purpose, a parametric fatigue life prediction model, proposed by Fawaz and Ellyin, was coupled with a global optimization technique, Particle Swarm Optimization (PSO), which is a meta-heuristic optimization algorithm. The number of distinct fiber orientation angles and the number of plies each lamina contains were predetermined. The fiber orientation angles in each layer were taken as design variables and determined in the design process. A number of problems were solved to demonstrate the effectiveness and reliability of the proposed method. (C) 2012 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of Noorul Islam Centre for Higher Education.Öğe Optimization of fiber-reinforced laminates for a maximum fatigue life by using the particle swarm optimization. Part I(Springer, 2013) Ertas, Ahmet H.In practice, the problems connected with the fatigue of composites are intricate because of their complex structure and the fatigue loading. Fatigue tests under different fiber orientation angles are time-consuming and also very expensive. Therefore, it is important to establish a technique to consider the fatigue damage at any fiber orientation angle without having to perform excessive amounts of testing. The general purpose is to elaborate a methodology for finding a globally optimum design of composite laminates subjected to in-plane loads. In this part of the study, the Fawaz-Ellyin model of fatigue life prediction is presented and further validated. The results obtained show that the model can be applied to optimization problems of composites.Öğe Optimization of Fiber-Reinforced Laminates for a Maximum Fatigue Life by Using the Particle Swarm Optimization. Part II(Springer, 2013) Ertas, Ahmet H.An improved methodology, with considering experimental results and numerical models, is proposed to find globally optimum designs of composite laminates subject to given in-plane loads for a maximum fatigue life. For this purpose, the Fawaz-Ellyin parametric fatigue-life prediction model was coupled with a global optimization technique, the particle swarm optimization, which is a metaheuristic optimization algorithm. The number of distinct fiber orientation angles and the number of plies in each lamina were predetermined. The fiber orientation angles in each layer were taken as design variables and determined in the design process. A number of problems were solved to demonstrate the efficiency and reliability of the method proposed.
